Air Con tripping on/off by itself with engine revs- 2.0HDI

[pugface406lx]

Hi there,

I have a problem with my W reg 2.0 hdi 406, the Air con keeps tripping out when my engine is revved up and then when it slows to idle like at a junction for example I can hear it tripping back on and the compressor starting up again. I wondered why it didnt seem to get that cold in the cabin and now I know whats going on.
I had a new condensor fitted last year as it wasnt working at all and then all seemed well until just recently.

Any help gratefully received before I end up armed with no knowledge at an air con specialist..!!

Thanks
Pugface

[steve_earwig]

That seems a bit bass-ackwards, if it was low on pressure then you'd think revving it would boost it and then it would work. Then I'm not really sure how these things work but a swift Google later and the suggestions are either the clutch is slipping (not sure how you'd test this) or it's been over-charged and the high-pressure cut out (if it has one that is) is cutting off the power.

[Doggy]

Worth checking out the connections to the a/c compressor clutch, might also indicate fluctuating pressure / bad connection at pressure switch, or a faulty relay in the BSI, (if your car has one).

[Welly]

It is perfectly normal for the compressor to cycle on/off with whilst it maintains pressure (all good systems do this to conserve your fuel) BUT if it's been gassed wrongly it will mess about and you won't get consistant cooling.

Try taking temperatures at the face vents on full cooling (Auto mode @ 14deg C) as long as the cabin is hot and it's warm outside then full cooling should get you a consistant 4 to 6 deg from the vents. Actually I observed the lowest temps whilst stationary and concluded the compressor runs flat out whilst stationary in traffic etc which makes sense to me as the heat gains are higher in/around the car.

If the temps are all over the shop then it's not right.

It should take about 10 minutes to get down to the 5's here was mine at 4.7 (I even had a 3.6 once)



I've just thought aswell - there is a sequence of events that can switch off the a/c automatically and these are at full engine load (heavy throttle over certain distance) to release load on the engine and also when the coolant temperature reading is too high (again for same reason). Maybe you've got a dodgy sensor somehow? I think I would first conclude whether the a/c has the correct gas pressure (the a/c place should check this for you) and then maybe get a decent code read for any signs of invalid readings going on?